Radio frequency-transmissive compositions, methods of forming radio frequency-transmissive compositions, microelectronic devices, wireless radio frequency communication devices, and methods of forming microelectronic devices, wireless radio frequency communication devices

ABSTRACT

Radio frequency-transmissive compositions having reduced dissipation factors, microelectronic devices, and in particular, wireless radio frequency communication devices which utilize such compositions, and methods of forming the same are described. In one implementation, a liquid resin is provided and a solid organic polymer filler material is provided within the resin to impart a degree of radio frequency transmissivity which is greater than that of the resin alone, i.e. the composition has a reduced dissipation factor. An exemplary resin comprises epoxy and an exemplary filler material is a polytetrafluoroethylene powder. In another implementation, such composition is formed or applied over a substrate which includes an antenna formed thereon and cured to provide a solid coating. The substrate can also have integrated circuitry and a battery mounted thereon to provide a wireless communication device. In such a case, the composition can be formed over and cured atop the integrated circuitry and the battery.

TECHNICAL FIELD

[0001] This invention relates to radio frequency-transmissivecompositions having reduced dissipation factors and methods of formingthe same. The invention also concerns microelectronic devices, and inparticular, wireless radio frequency communication devices which utilizesuch compositions, and methods of forming the same.

BACKGROUND OF THE INVENTION

[0002] Some microelectronic devices are designed for wirelesscommunication. Typically, such devices operate within a desired range ofradio frequencies. In designing such devices, consideration must begiven to the various materials which are utilized because of theirpotential to adversely impact device operation and performance. Forexample, some wireless microelectronic devices include antennas whichare utilized to send and receive electronic signals which fall withinthe desired range of frequencies. These antennas can be covered with amaterial which serves to protect the antenna from the externalenvironment. Yet in protecting the antenna, such materials by virtue oftheir physical characteristics may undesirably affect the ability of thedevice (and antenna) to transmit and receive electronic signals withinthe desired range of radio frequencies, i.e. such material may cause thesignals to be attenuated or undesirably dissipated. Such materials canalso affect the electromagnetic characteristics of such antennas such asthe antenna's resonant frequency.

[0003] Some microelectronic communication devices are very small and canbe covered with a protectant which effectively seals the device. As withthose materials which can adversely affect an antenna's operation bycovering all or a portion thereof, such protectants can also have animpact on overall device operation. Thus it is not enough to select aprotectant which only serves to protect or seal the device. Rather, thedesigner must consider all of the operation-impacting ramifications of aparticular material when it is selected for use with a particulardevice.

[0004] This invention arose out of concerns associated with providingmaterials and methods of forming materials which have desirableradio-frequency transmissivity characteristics. This invention alsoarose out of concerns associated with providing microelectronic devices,and in particular, wireless radio frequency communication devices whichutilize such materials, and methods of forming the same.

SUMMARY OF THE INVENTION

[0005] Radio frequency-transmissive compositions having reduceddissipation factors, microelectronic devices, and in particular,wireless radio frequency communication devices which utilize suchcompositions, and methods of forming the same are described. In oneimplementation, a liquid resin is provided and a solid organic polymerfiller material is provided within the resin to impart a degree of radiofrequency transmissivity which is greater than that of the resin alone,i.e. the composition has a reduced dissipation factor. An exemplaryresin comprises epoxy and an exemplary filler material is apolytetrafluoroethylene powder. In another implementation, suchcomposition is formed or applied over a substrate which includes anantenna formed thereon and cured to provide a solid coating. Thesubstrate can also have integrated circuitry and a battery mountedthereon to provide a wireless communication device. In such a case, thecomposition can be formed over and cured atop the integrated circuitryand the battery.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Preferred embodiments of the invention are described below withreference to the following accompanying drawings.

[0007]FIG. 1 is a flow diagram which illustrates certain methodicalaspects of the invention.

[0008]FIG. 2 is a flow diagram which illustrates certain methodicalaspects of the invention.

[0009]FIG. 3 is a top plan view of a wireless communication deviceconstructed in accordance with one aspect of the present invention.

[0010]FIG. 4 is a top plan view of the FIG. 3 device at a processingstep subsequent to that shown in FIG. 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] This disclosure of the invention is submitted in furtherance ofthe constitutional purposes of the U.S. Patent Laws “to promote theprogress of science and useful arts” (Article 1, Section 8).

[0012] Referring to FIG. 1, a flow diagram illustrates certainmethodical aspects of the invention generally at 10. A liquid resin orencapsulating material which is radio frequency transmissive to a firstdegree is provided at 12. Such resin has a first radio frequencydissipation factor. Exemplary resins include various epoxies, urethane,acrylic, polyester, and/or silicone. The resin can also include ahardener. As used in this document, the term “resin” will be understoodto include resins, such as those mentioned above, which may or may notinclude a hardener or hardening agent. An exemplary epoxy resin is R3500available from Epic Resins, Inc. of Palmyra, Wis. An exemplary EpicResin hardener is H5039. The hardener can also comprise a pre-blendedhardener having constituent parts of Epic Resin H5064 (25%) and K2400(75%). Another exemplary resin is Grace Specialty Polymers Stycast®#1267 which is available through W. R. Grace & Co. of Atlanta, Ga.

[0013] Filler material is provided into or within the liquid resin at 14to form a resin composition at 16 which is radio frequency transmissiveto a second degree which is greater than the first degree. Accordingly,the resin composition has a second radio frequency dissipation factorwhich is less than the first dissipation factor. In a preferredimplementation, such filler material constitutes a solid, such as anorganic polymer powder which is provided into the liquid resin in solidform and constitutes a plurality of particles which are suspendedtherewithin. Such suspended particles can have exemplary sizes frombetween 1-25 μm. Exemplary materials for the organic polymer fillerinclude the following: polytetrafluoroethylene, fluorinated ethylenepropylene, polypropylene, polystyrene, and/or polybutylene, withpowdered polytetrafluoroethylene being preferred. An exemplary powderedpolytetrafluoroethylene material is MP1100 Teflon® powder which isavailable from DuPont. The manufacturer of the resin could of coursesupply the filler material premixed in the resin, hardener, orresin/hardener composition.

[0014] The preferred resin composition or liquid mixture (pre-cure)preferably comprises between about 10% to 90% by volume of the organicpolymer filler material and even more preferably, between about 40% to70%. Such provides a flowable mixture which is formed or applied at 18over a suitable substrate, an exemplary one of which is described inmore detail below in connection with FIG. 2. An exemplary flowablemixture comprises the Epic Resin resin R3500 with a pre-blended hardenerhaving constituent parts of Epic Resin hardener H5064 (25%) and K2400(75%), with a 14% by-weight concentration of the DuPont MP1100 Teflon®powder. Thereafter, such flowable mixture can be exposed to conditionsat 20 which are effective to harden the flowable mixture into a solidmass or rigidified coating thereover.

[0015] Referring to FIG. 2, a substrate is provided at 22. An exemplarysubstrate comprises a polyester film having a thickness of around 5mils. An antenna is provided over or on the substrate at 24. In apreferred embodiment, such antenna is formed from conductiveantenna-forming material which is printed on the substrate. Suchantenna-forming material can constitute any suitable conductivematerial, with an exemplary material being a silver-filled material.Integrated circuitry can also be provided over or mounted on thesubstrate and operably connected with the antenna at 26. The integratedcircuitry can be configured for radio frequency operation within adesired range of frequencies. In one aspect, the integrated circuitryconstitutes at least one circuit comprising a radio frequency receiverand transmitter. A battery can also be provided at 28 and supported bythe substrate. Such battery is preferably operably connected with theintegrated circuitry to provide power thereto.

[0016] Referring to FIG. 3, an exemplary micro electronic radiofrequency communication device is shown at 30 and includes a substrate32 and an antenna 34 which is formed thereover as discussed above.Integrated circuitry, in the form of a semiconductor chip 36, is mountedon and supported by substrate 32. Antenna 34 is operably connected withsemiconductor chip 36 and configured therewith to operate relative todesired radio frequencies. A exemplary range of frequencies can bebetween 1 GHz and 30 GHz. More preferably, the desired frequency ofoperation is about 2.45 GHz. A battery 38 is provided and supportedrelative to substrate 32. Accordingly, such substrate constitutes acommon substrate which supports chip 36, antenna 34, and battery 38. Anexemplary microelectronic radio frequency communication device isdisclosed in U.S. patent application Ser. No. 08/705,043, which namesJames O'Toole, John R. Tuttle, Mark E. Tuttle, Tyler Lowrey, KevinDevereaux, George Pax, Brian Higgins, Shu-Sun Yu, David Ovard and RobertRotzoll as inventors, which was filed on Aug. 29, 1996, and is assignedto the assignee of this patent application.

[0017] Referring to FIG. 4, a liquid mixture or filled resin compositionis provided as described above, and formed or coated over at least aportion of, and preferably the entirety of antenna 34, chip 36, andbattery 38. Such is then cured into a solid mass or coating 40. In apreferred aspect, the curing is conducted at a temperature less than orequal to about 120° C. Even more preferred, in a communication systemwhich incorporates a battery, lower curing temperatures of between about40° C. and 80° C. could be utilized to reduce the possibility ofadversely affecting battery electrolyte material, some of which can boilat temperatures above 92° C.

[0018] The above described coating compositions provide a desired degreeof radio frequency transmissivity such that when incorporated intowireless communication devices, less of a radio frequency signal isdissipated than would otherwise be possible without the composition.Such is desirable from the standpoint of preserving the integrity and/orstrength of a particular signal. For example, some wirelesscommunication devices can utilize microwave backscatter as a means ofcommunicating between separated locations. Having such a deviceencapsulated with a material which is formed in accordance with theinvention can increase the efficiency with which a signal is passed toand from the device.

[0019] In compliance with the statute, the invention has been describedin language more or less specific as to structural and methodicalfeatures. It is to be understood, however, that the invention is notlimited to the specific features shown and described, since the meansherein disclosed comprise preferred forms of putting the invention intoeffect. The invention is, therefore, claimed in any of its forms ormodifications within the proper scope of the appended claimsappropriately interpreted in accordance with the doctrine ofequivalents.

1. A method of forming a radio-frequency-transmissive compositioncomprising: providing a liquid resin which is radio frequencytransmissive to a first degree; and providing an organic polymer fillermaterial within the liquid resin to form a resin composition which isradio frequency transmissive to a second degree which is greater thanthe first degree.
 2. The method of claim 1 , wherein the organic fillermaterial is a solid.
 3. The method of claim 1 , wherein the liquid resincomprises epoxy.
 4. The method of claim 1 , wherein the liquid resincomprises urethane.
 5. The method of claim 1 , wherein the liquid resincomprises acrylic.
 6. The method of claim 1 , wherein the liquid resincomprises polyester.
 7. The method of claim 1 , wherein the liquid resincomprises silicone.
 8. The method of claim 1 , wherein the organicpolymer filler material comprises a polymer powder.
 9. The method ofclaim 1 , wherein the organic polymer filler material comprisespolytetrafluoroethylene.
 10. The method of claim 1 , wherein the organicpolymer filler material comprises fluorinated ethylene propylene. 11.The method of claim 1 , wherein the organic polymer filler materialcomprises polypropylene.
 12. The method of claim 1 , wherein the organicpolymer filler material comprises polystyrene.
 13. The method of claim 1, wherein the organic polymer filler material comprises polybutylene.14. The method of claim 1 , wherein the resin composition comprisesbetween about 10% to 90% by volume of the organic polymer fillermaterial.
 15. The method of claim 1 , wherein the resin compositioncomprises between about 40% to 70% by volume of the organic polymerfiller material.
 16. The method of claim 1 further comprising curing theresin composition into a solidified mass.
 17. A method of forming aradio-frequency-dissipation-factor-reduced composition comprising:providing a liquid resin having a first radio frequency dissipationfactor; and providing an organic polymer filler material within theliquid resin to form a filled resin composition having a second radiofrequency dissipation factor which is less than the first dissipationfactor.
 18. The method of claim 17 , wherein the organic polymer fillermaterial is a solid.
 19. A method of forming a microelectronic devicecomprising: providing integrated circuitry supported by a substrate;providing a liquid resin having an organic polymer filler materialtherein, wherein the organic polymer filler material is solid asprovided within the liquid resin; applying the resin having the organicpolymer filler material over at least a portion of the substrate andintegrated circuitry; and curing the applied resin into a solid mass.20. The method of claim 19 , wherein the organic polymer filler materialcomprises a polymer powder.
 21. The method of claim 19 , wherein theorganic polymer filler material comprises polytetrafluoroethylene. 22.The method of claim 19 , wherein the organic polymer filler materialincludes at least one of the following: polytetrafluoroethylene,fluorinated ethylene propylene, polypropylene, polystyrene, andpolybutylene.
 23. The method of claim 19 , wherein the liquid resinincludes at least one of the following: epoxy, urethane, acrylic,polyester, and silicone.
 24. The method of claim 19 , wherein the liquidresin comprises between about 10% and 90% by volume of the organicpolymer filler material.
 25. The method of claim 19 , wherein the liquidresin comprises between about 40% and 70% by volume of the organicpolymer filler material.
 26. The method of claim 19 , wherein the curingof the applied resin is conducted at a temperature less than or equal to120° C.
 27. The method of claim 19 further comprising: providing anantenna on the substrate; and operably connecting the antenna and theintegrated circuitry to provide a device configured for RF operation.28. A method of forming a microelectronic device comprising: providing aliquid encapsulating material having a first RF-associated dissipationfactor; mixing a material having a second RF-associated dissipationfactor which is less than the first RF-associated dissipation factorinto the liquid encapsulating material to provide a liquid mixturehaving an effective RF-associated dissipation factor which is less thanthe first RF-associated dissipation factor; applying the liquid mixtureover a substrate having microelectronic circuitry configured for RFoperation thereon; and curing the liquid mixture into a solid coating.29. The method of claim 28 , wherein the material having the secondRF-associated dissipation factor comprises a solid.
 30. The method ofclaim 28 , wherein the liquid encapsulating material comprises an epoxy.31. The method of claim 30 , wherein the liquid encapsulating materialcomprises a hardener.
 32. The method of claim 28 , wherein the materialhaving the second RF-associated dissipation factor comprises a polymerpowder.
 33. The method of claim 32 , wherein the polymer powdercomprises polytetrafluoroethylene.
 34. The method of claim 28 , whereinthe applying of the liquid mixture comprises covering themicroelectronic circuitry therewith.
 35. A method of forming amicroelectronic radio frequency communication device comprising:providing integrated circuitry and an antenna operably connectedtherewith and configured to transmit and receive radio frequencysignals; providing a liquid polymer resin having a first radio frequencydissipation factor and a polymer powder therewithin having a secondradio frequency dissipation factor which is less than the first radiofrequency dissipation factor; coating at least a portion of the antennaand the integrated circuitry with the liquid polymer resin having thepolymer powder therewithin; and curing the coated liquid polymer resinhaving the polymer powder to form a solid coating having a radiofrequency dissipation factor which is less than the first radiofrequency dissipation factor.
 36. The method of claim 35 , wherein thecoating comprises coating the entire antenna with the liquid polymerresin having the polymer powder therewithin.
 37. The method of claim 35, wherein the providing of the integrated circuitry and the antennacomprises: printing conductive antenna-forming material on a substrate;and mounting an integrated circuitry chip on the substrate.
 38. Themethod of claim 37 , wherein the coating comprises coating the entireantenna with the liquid polymer resin having the polymer powdertherewithin.
 39. The method of claim 35 , wherein the liquid polymerresin comprises an epoxy.
 40. The method of claim 35 , wherein thepolymer powder comprises polytetrafluoroethylene.
 41. The method ofclaim 35 , wherein the liquid polymer resin and the polymer powdercomprise a liquid mixture having, before the curing, between about 10%to 90% by volume of the polymer powder.
 42. The method of claim 35 ,wherein the liquid polymer resin and the polymer powder comprise aliquid mixture having, before cure, between about 40% to 70% by volumeof the polymer powder.
 43. The method of claim 35 , wherein the curingcomprises curing the coated liquid polymer resin having the polymerpowder at a temperature of less than or equal to 120° C.
 44. A method offorming a microelectronic radio frequency communication devicecomprising: supporting a semiconductor chip, at least one antenna, and abattery relative to a common substrate; the chip, antenna, and batterybeing operably interconnected and configured to operate relative to atleast one desired radio frequency; forming a flowable mixture comprisinga resin and at least one organic polymer filler material suspendedtherewithin, the one filler material being frequency-transmissive to adesired degree relative to said at least one desired radio frequency;and forming the flowable mixture over at least a portion of the deviceand thereafter exposing the flowable mixture to conditions which areeffective to harden the flowable mixture into a solid coating thereover.45. The method of claim 44 , wherein the at least one desired frequencycomprises a frequency in a range between 1 GHz and 30 GHz.
 46. Themethod of claim 45 , wherein the at least one desired frequency is about2.45 GHz.
 47. The method of claim 44 , wherein the at least one organicpolymer filler material comprises a polymer powder.
 48. The method ofclaim 47 , wherein the polymer powder comprises polytetrafluoroethylene.49. The method of claim 47 , wherein the resin comprises an epoxy. 50.The method of claim 47 , wherein the forming of the flowable mixturecomprises forming the mixture over the entire antenna.
 51. The method ofclaim 47 , wherein the forming of the flowable mixture comprises formingthe mixture over the entire device.
 52. A method of forming amicroelectronic communication device comprising: supporting asemiconductor chip relative to a substrate; supporting an antennarelative to the substrate, the antenna being operably connected with thechip and configured therewith to operate relative to at least onedesired radio frequency; and covering the chip and substrate with arigidified coating of material having a plurality of organic polymericparticles suspended therewithin, said particles imparting a degree offrequency transmissivity to the coating relative to said at least onedesired radio frequency which is higher than the coating would havewithout said particles.
 53. The method of claim 52 further comprising:prior to the covering of the chip and substrate, forming a liquidmixture comprising the organic polymeric particles; and wherein thecovering of the chip and substrate comprises curing the liquid mixtureover the chip and substrate.
 54. A method of forming a radio frequencyidentification device comprising: providing a circuit comprising a radiofrequency receiver and transmitter; operably connecting an antenna withthe circuit, the antenna being configured to receive and transmit atleast one desired radio frequency; and coating the antenna and at leastsome of the circuit with a coating material comprising a resin havingsolid polymeric material therewithin, the resin having a first radiofrequency transmissivity value and the polymeric material imparting asecond radio frequency transmissivity value to the coating materialwhich is greater than the first radio frequency transmissivity value.55. The method of claim 54 , wherein the solid polymeric materialcomprises an organic powder.
 56. The method of claim 54 , wherein thesolid polymeric material comprises powdered polytetrafluoroethylene. 57.A radio-frequency-transmissive composition comprising: a liquid resinwhich is radio frequency transmissive to a first degree; and a solidorganic polymer filler material disposed within the liquid resin to forma resin composition which is radio frequency transmissive to a seconddegree which is greater than the first degree.
 58. Theradio-frequency-transmissive composition of claim 57 , wherein theorganic polymer filler material comprises a polymer powder.
 59. A radiofrequency microelectronic device comprising: a substrate; integratedcircuitry supported by the substrate and configured for radio frequencyoperation; and a solid mass disposed over the substrate and at least aportion of the integrated circuitry, the solid mass comprising acomposition having a suspension of organic polymer filler materialtherewithin.
 60. The radio frequency microelectronic device of claim 59further comprising an antenna disposed over the substrate, the solidmass being disposed over the antenna.
 61. The radio frequencymicroelectronic device of claim 59 , wherein the organic polymer fillermaterial comprises polytetrafluoroethylene.
 62. A microelectronic radiofrequency communication device comprising: a substrate; a semiconductorchip supported by the substrate; at least one antenna supported by thesubstrate and operably connected with the semiconductor chip; a batterysupported by the substrate and operably connected with the semiconductorchip; and a solid coating of material disposed over the antenna andcomprising an organic polymer material.
 63. The microelectronic radiofrequency communication device of claim 62 , wherein the organic polymermaterial comprises a polymer powder.
 64. The microelectronic radiofrequency communication device of claim 62 , wherein the organic polymermaterial comprises polytetrafluoroethylene.
 65. The microelectronicradio frequency communication device of claim 62 , wherein the solidcoating is disposed over the entire substrate and effectively seals thesemiconductor chip, the antenna, and the battery relative to thesubstrate.